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In computer programming, a variable-length array (VLA), also called variable-sized or runtime-sized, is an array data structure whose length is determined at runtime, instead of at compile time. [1] In the language C , the VLA is said to have a variably modified data type that depends on a value (see Dependent type ).
C++ enforces stricter typing rules (no implicit violations of the static type system [1]), and initialization requirements (compile-time enforcement that in-scope variables do not have initialization subverted) [7] than C, and so some valid C code is invalid in C++. A rationale for these is provided in Annex C.1 of the ISO C++ standard.
C struct data types may end with a flexible array member [1] with no specified size: struct vectord { short len ; // there must be at least one other data member double arr []; // the flexible array member must be last // The compiler may reserve extra padding space here, like it can between struct members };
The g++ compiler implements the multiple inheritance of the classes B1 and B2 in class D using two virtual method tables, one for each base class. (There are other ways to implement multiple inheritance, but this is the most common.) This leads to the necessity for "pointer fixups", also called thunks, when casting. Consider the following C++ code:
C99 introduced "variable-length arrays" which address this issue. The following example using modern C (C99 or later) shows allocation of a two-dimensional array on the heap and the use of multi-dimensional array indexing for accesses (which can use bounds-checking on many C compilers):
Cover of the C99 standards document. C99 (previously C9X, formally ISO/IEC 9899:1999) is a past version of the C programming language open standard. [1] It extends the previous version with new features for the language and the standard library, and helps implementations make better use of available computer hardware, such as IEEE 754-1985 floating-point arithmetic, and compiler technology. [2]
C has the ability to initialize arrays of arbitrary length. The sizeof operator can be used to obtain the size of a statically initialized array in C code. For instance, in the following code, the terminating index for the loop automatically adjusts should the list of strings be changed.
A tracking reference in C++/CLI is a handle of a passed-by-reference variable. It is similar in concept to using *& (reference to a pointer) in standard C++, and (in function declarations) corresponds to the ref keyword applied to types in C#, or ByRef in Visual Basic .NET. C++/CLI uses a ^% syntax to indicate a tracking reference to a handle.